The exemplary embodiments relate generally to the processing of integrated circuits and, more particularly, relate to the processing of photonics devices integrated into the processing of integrated circuits.
Optical interconnects can offer significant advantages over electrical circuitry in the field of advanced microelectronics. One possible implementation of an optical interconnect system is based on silicon-on-insulator (SOI) technology, in which optical waveguides are formed on the same thin silicon layer as other complimentary-metal-oxide-semiconductor (CMOS) circuit elements (e.g., field effect transistors (FETs), capacitors, resistors, etc.). Light sources produce optical signals (e.g., light pulses) that propagate in these optical waveguides. Photodetectors convert the optical signals into electrical signals.
The integration of germanium into a conventional CMOS process is complicated by the additional thermal budget required by germanium growth, the maximum temperature germanium can withstand, cross-contamination issues, germanium doping issues, germanium passivation issues, and the tendency of germanium to form non-ohmic contacts when mated with those metallic materials conventionally used for vertical contacts. There is a need, as a result, for structures and process integration schemes that overcome some or all of these issues and allow waveguides and germanium photodetectors to be effectively fabricated in a manner that is compatible with conventional CMOS processing.